The subject matter disclosed herein relates to gas turbines and, in particular, to fuel injection for gas turbine combustors.
In a typical combustor for a gas turbine, fuel is introduced by cross flow injection with respect to an input air stream. A relatively small reduction in the magnitude and/or severity of the issues associated with cross flow injection can be achieved by varying the angle of the fuel jet, and/or by using non-conventional designs for the fuel discharge holes. Nevertheless, a fuel jet in cross flow creates a recirculation zone or bubble located behind the fuel jet. The size of this recirculation bubble depends on many factors, including jet diameter and momentum ratio between the jet and mainstream flow. The recirculation bubble normally increases in size with the diameter and momentum of the fuel jet. When a fuel jet is introduced in cross flow, fuel may become entrained behind the fuel jet, leading to a flammable mixture in the recirculation zone or bubble behind the jet. Flame holding can occur in this region, leading to hardware damage. Also, a boundary layer disruption by the fuel jet can lead to flow separation on the nozzle center body, on the vane, and in the diffusers. A propensity to a fuel rich boundary layer, which leads to flame holding or flashback, also exists.